The results of our recent studies suggest that endogenous viral mechanisms exist which promote cleavage of structural proteins and enzyme activation along specific pathways. These studies suggest that viral uncoating and activation of initial replicative events are not entirely host-mediated functions, as presently assumed. The objective of this proposal is to determine whether activation by protein cleavage is used in conjunction with other covalent modifications, such as phosphorylation and glycosylation, to induce new enzymatic functions after virus infection. The fate of infecting virus containing radioactive protein will be followed during adsorption, penetration, and initial phases of infection. Infected cell extracts will be prepared, fractionated by equilibrium centrifugation in discontinuous sucrose gradients, and analyzed for the presence of parental subviral particles which differ from each other with respect to modification state of cleaved, phosphorylated and glycosylated proteins, and functional state of virion associated methylases and mRNA transcriptase.